The present invention relates to thermoplastic molding compositions comprising    A) from 40 to 96% by weight of a semiaromatic polyamide,    B) from 2 to 30% by weight of a copolymer composed of            B1) from 35 to 89.9% by weight of ethylene,        B2) from 10 to 60% by weight of 1-octene or 1-butene or propylene or a mixture of these, and        B3) from 0.05 to 5% by weight of functional monomers, where the functional monomers have been selected from the group of the carboxylic acid groups, carboxylic anhydride groups, carboxylic ester groups, carboxamide groups, carboximide groups, amino groups, hydroxy groups, epoxy groups, urethane groups, or oxazoline groups, or a mixture of these,            C) from 1 to 50% by weight of fibrous or particulate fillers, or a mixture of these,    D) from 0.1 to 10% by weight of            D1) at least one highly branched or hyperbranched polycarbonate with an OH number of from 1 to 600 mg KOH/g of polycarbonate (to DIN 53240, part 2), or        D2) at least one highly branched or hyperbranched polyester of AxBy type, where x is at least 1.1 and y is at least 2.1,        or a mixture of these,            E) from 0 to 15% by weight of an electrically conductive additive,    F) from 0 to 30% by weight of further additives,where the total of the percentages by weight of components A) to F) is 100%.
The present invention moreover relates to the use of these molding compositions for production of moldings of any type, and to the resultant moldings, preferably motor vehicle bodywork parts of any type.
Polymer blends based on polyamides and on polyphenylene ethers are used as a material for bodywork parts, because they have high heat resistance. Such products are marketed by way of example by GEP as Nory®GTX. A disadvantage for the use as bodywork material is the comparatively high fall-off in stiffness under ambient conditions.
DE-A 101 49 152 describes thermoplastic molding compositions based on polyamides, on graft rubbers of ABS type, and on fine-particle fillers, as a material for bodywork parts. Such products are marketed by way of example by Lanxess with the trademark Triax®. While the stiffness of these products is higher than that of Noryl®GTX, the toughness of this material is in most cases inadequate.
WO 2004/056919 discloses conductive thermoplastic molding compositions which comprise mixtures of various conductivity additives.
WO 2004/048452 discloses conductive thermoplastic molding compositions based on polyamides, graft copolymers, and antistatic agents. These products likewise have low impact resistance.
WO 2006/42705 discloses PA molding compositions which comprise highly branched or hyperbranched polymers as flow improvers.
It was therefore an object of the present invention to provide thermoplastic PA molding compositions which have improved flowability and also demoldability, together with better low-temperature impact resistance.
This object is achieved via the molding compositions defined in the introduction. Preferred embodiments are found in the subclaims.
Surprisingly, the inventive molding compositions have not only improved flowability but also markedly improved ductility at −30° C.
The inventive molding compositions comprise, as component A), from 40 to 96% by weight, preferably from 45 to 92% by weight, and in particular from 50 to 91% by weight, of at least one semiaromatic polyamide.
Preference is given to those semiaromatic copolyamides, such as PA 6/6T and PA 66/6T, whose triamine content is less than 0.5% by weight, preferably less than 0.3% by weight (see EPA 299 444).
The preferred semiaromatic copolyamides having low triamine content can be prepared by the processes described in EP-A 129 195 and 129 196.
The inventive thermoplastic molding compositions comprise, as component A), at least one semiaromatic copolyamide having the structure described below:
The semiaromatic copolyamides A) comprise, as component a1), from 40 to 90% by weight of units which derive from terephthalic acid and hexamethylenediamine. A small proportion of the terephthalic acid, preferably not more than 10% by weight of the entire aromatic dicarboxylic acids used, can be replaced by isophthalic acid or other aromatic dicarboxylic acids, preferably those in which the carboxy groups are in para-position.
Alongside the units which derive from terephthalic acid and hexamethylenediamine, other units present in the semiaromatic copolyamides are units derived from ε-caprolactam (a2) and/or units which derive from adipic acid and hexamethylenediamine (a3).
The proportion of units which derive from ε-caprolactam is at most 50% by weight, preferably from 20 to 50% by weight, in particular from 25 to 40% by weight, while the proportion of units which derive from adipic acid and hexamethylenediamine is up to 60% by weight, preferably from 30 to 60% by weight, and in particular from 35 to 55% by weight.
The copolyamides can also comprise not only units of ε-caprolactam but also units of adipic acid and hexamethylenediamine; in this case, care has to be taken that the proportion of units free from aromatic groups is at least 10% by weight, preferably at least 20% by weight. There is no particular restriction here on the ratio of the units which derive from ε-caprolactam and from adipic acid and hexamethylenediamine.
Polyamides having from 50 to 80% by weight, in particular 60 to 75% by weight, of units which derive from terephthalic acid and hexamethylenediamine (units a1)) and from 20 to 50% by weight, preferably from 25 to 40% by weight, of units which derive from ε-caprolactam (units a2)) have proven particularly advantageous for many applications.
The inventive semiaromatic copolyamides can also comprise, alongside the units a1) to a3) described above, subordinate amounts, preferably not more than 15% by weight, in particular not more than 10% by weight, of further polyamide units (a4) known from other polyamides. These units can derive from dicarboxylic acids having from 4 to 16 carbon atoms and from aliphatic or cycloaliphatic diamines having from 4 to 16 carbon atoms, or else from aminocarboxylic acids and, respectively, corresponding lactams having from 7 to 12 carbon atoms. To mention just a few suitable monomers of these types: suberic acid, azelaic acid, sebacic acid or isophthalic acid as representatives of the dicarboxylic acids, 1,4-butanediamine, 1,5-pentanediamine, piperazine, 4,4′-diaminodicyclohexylmethane, 2,2-(4,4′-diaminodicyclohexyl)propane or 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane as representatives of the diamines, and caprylolactam, enantholactam, omega-aminoundecanoic acid and laurolactam as representatives of lactams or aminocarboxylic acids.
The melting points of the semiaromatic copolyamides A) are in the range from 260 to above 300° C., and this high melting point is also attended by a high glass transition temperature which is generally more than 75° C., in particular more than 85° C.
The melting points of binary copolyamides based on terephthalic acid, hexamethylenediamine, and ε-caprolactam, given contents of about 70% by weight of units which derive from terephthalic acid and hexamethylenediamine, are in the region of 300° C., their glass transition temperature being more than 110° C.
The melting points of binary copolyamides based on terephthalic acid, adipic acid, and hexamethylenediamine (HMD), even at relatively low contents of about 55% by weight of units composed of terephthalic acid and hexamethylenediamine reach 300° C. and more, but the glass transition temperature is not quite as high as for binary copolyamides which comprise ε-caprolactam instead of adipic acid or adipic acid/HMD.